This invention relates in general to fire protection systems for aircraft and more particularly to an improved control head which controls the discharge of fire extinguishing agent from a container in an aircraft fire extinguishing system.
Patent application Ser. No. 324,698, filed Nov. 25, 1981 by William A. Enk et al discloses an electronic system for controlling an aircraft fire protection system. As described in the application, the fire extinguishant material is contained in a series of bottles which can be selectively discharged by operating contols on a cabin mounted control panel. A series of solenoid valves direct the extinguishant to the area of the aircraft in which the fire is present.
Discharge of each extinguishant bottle is controlled by a control head on the end of the bottle. An electrical detonator in the control head can be activated to cause the bottle to discharge extinguishant material into the fluid delivery lines of the system. The various types of control heads that have been proposed in the past for fire extinguishing systems are not well suited for use in aircraft systems, primarily because they are not designed specifically for aircraft applications. For example, the device shown in U.S. Pat. No. 4,126,184 to Hinrichs is used in a fire suppression system for a commercial or industrial building. There is no particular concern for space or weight requirements in the Hinrichs design because such buildings are not subject to the same space and weight limitations that form major factors in aircraft designs. Hinrichs provides only one configuration which in many cases would not fit in the area available on an aircraft. Furthermore, the Hinrichs device is not exposed to temperatures as high as those that are often encountered in aircraft systems.
In all known control heads having an electrical detonator, periodic replacement of the detonator is required to conform with prevailing safety standards. Since the detonator and related components such as electrical leads and connectors are exposed to the ambient air and thus to possible contamination which can cause the detonator to malfunction, its useful life is relatively short and replacement is required at regular intervals. Possible contamination of the detonator also increases the maintenance requirements and decreases the reliability of the system, especially after the detonator has been in service for an extended period of time. If the container should develop a leak permitting the extinguishant to escape, the leak can remain undetected and the container may completely discharge so that its contents are not available when needed. Another problem in existing systems is that inadvertent discharge of the extinguishant bottles can occur.
Typically, existing fire extinguishant systems for buildings simply discharge the extinguishing agent from the bottle through a pipe and nozzle without additional control, as shown in the Hinrichs 4,126,184 patent. Therefore, foreign materials in the extinguishant such as fragments from the exploding rupture disks do not present significant problems. However, in an aircraft system such as shown in the aforementioned Enk et al application, valves are included to direct the extinguishant to the area of the fire. Metal fragments and other solid matter in the flow lines can jam the solenoid valves and cause other malfunctions. Accordingly, filtering of the fluid upstream from each valve is necessary in order to assure proper operation of the valves.